[JIRA] (JENKINS-41580) Branches gone missing after SCM-API upgrades applied

[email protected] (JIRA) Tue, 31 Jan 2017 02:15:02 -0800

Title: Message Title

So here is an example of where the job is failing to load:

 
                                                                Jan 30, 2017 10:27:16 PM com.cloudbees.hudson.plugins.folder.AbstractFolder loadChildren
WARNING: could not load /var/lib/jenkins/jobs/GitHub_Projects/jobs/Multibranch_1_quality-assurance_kshultzCB/branches/Laurinburg
java.lang.NullPointerException
	at jenkins.branch.Branch.getName(Branch.java:147)
	at jenkins.branch.MultiBranchProjectDescriptor$ChildNameGeneratorImpl.dirNameFromItem(MultiBranchProjectDescriptor.java:249)
	at jenkins.branch.MultiBranchProjectDescriptor$ChildNameGeneratorImpl.dirNameFromItem(MultiBranchProjectDescriptor.java:225)
	at com.cloudbees.hudson.plugins.folder.AbstractFolder.loadChildren(AbstractFolder.java:546)
	at com.cloudbees.hudson.plugins.folder.AbstractFolder.onLoad(AbstractFolder.java:702)
	at com.cloudbees.hudson.plugins.folder.computed.ComputedFolder.onLoad(ComputedFolder.java:171)
	at jenkins.branch.MultiBranchProject.onLoad(MultiBranchProject.java:166)
	at com.cloudbees.hudson.plugins.folder.AbstractFolder.loadChildren(AbstractFolder.java:597)
	at com.cloudbees.hudson.plugins.folder.AbstractFolder.onLoad(AbstractFolder.java:702)
	at com.cloudbees.hudson.plugins.folder.Folder.onLoad(Folder.java:107)
	at hudson.model.Items.load(Items.java:372)
	at jenkins.model.Jenkins$17.run(Jenkins.java:3067)
	at org.jvnet.hudson.reactor.TaskGraphBuilder$TaskImpl.run(TaskGraphBuilder.java:169)
	at org.jvnet.hudson.reactor.Reactor.runTask(Reactor.java:282)
	at jenkins.model.Jenkins$7.runTask(Jenkins.java:1066)
	at org.jvnet.hudson.reactor.Reactor$2.run(Reactor.java:210)
	at org.jvnet.hudson.reactor.Reactor$Node.run(Reactor.java:117)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at java.lang.Thread.run(Thread.java:745)
 
                                                            

Which is an NPE in this function:

 
                                                                    public String getName() {
        // TODO this could include a uniquifying prefix defined in BranchSource
        return head.getName();
    }

In other words, the head of a branch is null which should never happen

So let's look at the source data:

 
                                                                      <branch plugin="[email protected]">
        <sourceId>94242f50-b6ac-4f8e-8940-65b65c5fc8fd</sourceId>
        <scm class="hudson.plugins.git.GitSCM" plugin="[email protected]">
          <configVersion>2</configVersion>
          <userRemoteConfigs>
            <hudson.plugins.git.UserRemoteConfig>
              <name>origin</name>
              <refspec>+refs/heads/*:refs/remotes/origin/*</refspec>
              <url>https://github.com/kshultzCB/quality-assurance.git</url>
              <credentialsId>0ec1d5e6-012b-4273-a01b-a1efb4812384</credentialsId>
            </hudson.plugins.git.UserRemoteConfig>
            <hudson.plugins.git.UserRemoteConfig>
              <name>origin</name>
              <refspec>+refs/pull/*/head:refs/remotes/origin/pr/*</refspec>
              <url>https://github.com/kshultzCB/quality-assurance.git</url>
              <credentialsId>0ec1d5e6-012b-4273-a01b-a1efb4812384</credentialsId>
            </hudson.plugins.git.UserRemoteConfig>
          </userRemoteConfigs>
          <branches class="singleton-list">
            <hudson.plugins.git.BranchSpec>
              <name>Laurinburg</name>
            </hudson.plugins.git.BranchSpec>
          </branches>
          <doGenerateSubmoduleConfigurations>false</doGenerateSubmoduleConfigurations>
          <submoduleCfg class="empty-list"/>
          <extensions/>
        </scm>
        <properties/>
      </branch>
 
                                                            

So this was saved with branch-api 1.11.1 and git 3.0.1 (also workflow multibranch 2.9.2 which is outside of the snippet above) but critically it is missing the <head> entry

If we compare this seed data with my test data set, we see:

 
                                                                      <branch plugin="[email protected]">
        <sourceId>45f20856-e3d0-437c-93ad-1532be81fdf1</sourceId>
        <head plugin="[email protected]">
          <name>feature-1</name>
        </head>
        <scm class="hudson.plugins.git.GitSCM" plugin="[email protected]">
          <configVersion>2</configVersion>
          <userRemoteConfigs>
            <hudson.plugins.git.UserRemoteConfig>
              <name>origin</name>
              <refspec>+refs/heads/*:refs/remotes/origin/*</refspec>
              <url>https://github.com/cloudbeers/fu-manchu.git</url>
              <credentialsId>github</credentialsId>
            </hudson.plugins.git.UserRemoteConfig>
            <hudson.plugins.git.UserRemoteConfig>
              <name>origin</name>
              <refspec>+refs/pull/*/head:refs/remotes/origin/pr/*</refspec>
              <url>https://github.com/cloudbeers/fu-manchu.git</url>
              <credentialsId>github</credentialsId>
            </hudson.plugins.git.UserRemoteConfig>
          </userRemoteConfigs>
          <branches class="singleton-list">
            <hudson.plugins.git.BranchSpec>
              <name>feature-1</name>
            </hudson.plugins.git.BranchSpec>
          </branches>
          <doGenerateSubmoduleConfigurations>false</doGenerateSubmoduleConfigurations>
          <submoduleCfg class="empty-list"/>
          <extensions/>
        </scm>
        <properties class="java.util.concurrent.CopyOnWriteArrayList"/>
      </branch>
 
                                                            

We see the <head> entry which is what we expect.

Next let's take a look at the archive contents:

 
                                                                -rw-r--r--  0 jenkins jenkins  1887 30 Jan 19:11 var/lib/jenkins/jobs/GitHub_Projects/jobs/Multibranch_1_quality-assurance_kshultzCB/branches/Laurinburg/config.xml
...
-rw-r--r--  0 jenkins jenkins    10 30 Jan 18:08 var/lib/jenkins/jobs/GitHub_Projects/jobs/Multibranch_1_quality-assurance_kshultzCB/branches/Laurinburg/name-utf8.txt
-rw-r--r--  0 jenkins jenkins   396 30 Jan 18:08 var/lib/jenkins/jobs/GitHub_Projects/jobs/Multibranch_1_quality-assurance_kshultzCB/branches/Laurinburg/scm-revision-hash.xml

So the interesting thing here is the timestamps on name-utf8.txt and scm-revision-hash.xml compared with config.xml

Unless you have been changing your system clock, this looks very much like:

1. System upgraded to latest and ran an index at 18:08
2. System downgraded to pre-upgrade and ran an index or otherwise triggered a save of the branch config.xml at 19:11
3. Upgraded again.

If we look at the branch api 2.0.x tracking file: scm-revision-hash.xml we can see some more details:

 
                                                                <?xml version='1.0' encoding='UTF-8'?>
<jenkins.plugins.git.AbstractGitSCMSource_-SCMRevisionImpl plugin="[email protected]">
  <head class="org.jenkinsci.plugins.github_branch_source.BranchSCMHead" plugin="[email protected]">
    <name>Laurinburg</name>
  </head>
  <hash>d1ecb00aeb4d9dd482d7574c7e2c02116022caf6</hash>
</jenkins.plugins.git.AbstractGitSCMSource_-SCMRevisionImpl>
 
                                                            

So at 18:08 we know that the Git 3.0.2-beta-2 plugin and github branch source 2.0.1-beta-6 plugins were installed and that the head was of type org.jenkinsci.plugins.github_branch_source.BranchSCMHead

That type does not exist in the 1.x versions of GitHub Branch Source, so when downgrading to the pre-upgrade version the head will be resolved as null (because it is an unknown type) and then even when we upgrade again we will now have the null

It is for the above exact reason that we set compatibleSinceVersion == 2.0.0 which means that if you upgrade to this version you cannot downgrade without restoring from a backup as there are changes made to the configuration files on disk that will result in data loss during a downgrade below the indicated version

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[JIRA] (JENKINS-41580) Branches gone missing after SCM-API upgrades applied

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